Diesel Engines in the 900 to 6,600 HP range typically have fuel injection pumps capable of pressurizing fuel up to and over 30,000 psi. Historically, a fuel injection pump has been placed with an injector on each cylinder. Today, most manufacturers have switched to a single fuel injection pump and a high pressure accumulator, known as a “Common Rail.” In most applications, the fuel injection pump must be fed by a fuel transfer pump. The fuel transfer pump provides fuel to the fuel injection pump at a sufficient flow rate and pressure to allow for successful operation.
Historically, mechanically driven fuel transfer pumps have been the predominant method of fuel transfer, but not without problems.
For example, a typical mechanically driven fuel transfer pump normally has a dynamic shaft seal which prevents fuel from escaping into the engine or into the environment. This seal can become damaged by wear or debris and leak—creating a safety, reliability, and/or maintenance point.
Additionally, the mechanically driven fuel transfer pump RPM is directly tied to engine speed; however, fuel consumption is not always directly proportional to engine speed and, as a result, the pump must be sized for all possible combinations of fuel consumption and RPM. As a result, the pump provides much more flow than is needed most of the time. Accordingly, this extra flow normally is drained back to the fuel tank and the power required to pump the fuel up to pressure is lost thereby wasting energy.
A further problem with the mechanically driven fuel transfer pump RPM is that when the engine is cranking or idling (lowest RPM) the pump may not have enough lift capability to lift fuel from the main fuel tank to the fuel injection pump. This problem is made worse when the fuel tank is positioned significantly lower than the pump, as in locomotives, where the pump normally has to lift fuel at least 6 feet. This can prevent successful priming and keep fuel from reaching the fuel injection pump. To counter this problem, many manufacturers install a third priming pump that is either hand operated or electric motor driven for lifting fuel from the tank to the fuel transfer pump to prime it before cranking the engine. This creates added cost and complexity.
Today, electric motor driven fuel transfer pumps are an addition to the mechanically driven fuel transfer pumps and take the form of either a DC motor driven fuel transfer pump or an AC motor driven fuel transfer pump.
The DC motor driven fuel transfer pumps are problematic for a variety of reasons. First, a category of DC motor driven fuel transfer pumps utilize a dynamic shaft seal that is similar to the seal used in the mechanical version noted above thereby resulting in the same problem of the seal becoming damaged by wear or debris and resulting in a leak creating a safety, reliability, and/or maintenance point. Another problem associated with the DC motor driven fuel transfer pump is motor brush life. In applications such as locomotives, the pump is expected to operate for up to 10 years of continuous duty. This type of duty cycle results in numerous brush changes thereby increasing maintenance costs and chance of failure.
Current AC motor driven fuel transfer pumps operating in applications where only DC power is available accomplish this through a power inverter that creates an AC output from DC input to drive the AC motor.
The inverter for these pumps operates open loop, which means the controller drives the motor at a maximum RPM when maximum voltage is available. RPM can be slowed by lowering available voltage, but this is not practical when other components on the machine are dependent upon the full voltage. Fuel pressure is regulated by mechanical valves. In this case, as in all examples listed above, the pump is sized for maximum fuel consumption. In normal operation, when maximum fuel is not consumed, the fuel is bypassed back to the tank. This adds heat to the fuel and consumes more electrical power than what is actually required to deliver the necessary fuel and wears pump components faster than necessary. Furthermore, pumping excess fuel drives excessive filter sizing and expense.
For the foregoing reasons, there is a need for a fuel transfer pump that, inter alia, overcomes the significant shortcomings of the known prior-art as delineated hereinabove.
BRIEF SUMMARY OF THE INVENTION
In general, and in one aspect, an embodiment of the invention provides a pulse width modulated (PWM) fuel transfer pump system comprising a multi-mode control process for efficiently delivering fuel to a high pressure fuel injection pump under multiple modes of system and engine operation.
In another aspect, an embodiment of the invention provides a fuel transfer pump system that is a cost effective energy management system that operates on demand and under multiple modes of system and engine operation. Thus, there is a cost savings versus using prior conventional mechanically and electric motor driven fuel transfer pumps.
In another aspect, an embodiment of the invention provides a fuel transfer pump system that comprises an AC Induction motor and a multi-mode control process which dynamically controls the speed of the AC induction motor for delivering a target pressure of fuel to the high pressure fuel injection pump over a broad range of engine operating conditions. Hence, the fuel transfer pump system dynamically controls the delivery of fuel to the high pressure fuel injection pump as opposed to the static delivery of fuel by the prior conventional mechanically and electric motor driven fuel transfer pumps. Accordingly, this control can result in a reduction in filter size and/or extending filter life.
In another aspect, an embodiment of the multi-mode control process of the fuel transfer pump system dynamically switches between multiple modes of control as a function of engine start up, running, and shut down conditions and also as a function of anomalous conditions of operation.
In another aspect, an embodiment of the multi-mode control process of the fuel transfer pump system dynamically compensates for voltage fluctuations of the power source powering the system.
In another aspect, an embodiment of the invention provides a method for controlling a fuel transfer pump delivering fuel to a high pressure fuel injection pump; the method comprising: providing a fuel transfer pump having an inlet port which is connectable in fluid communication with a fuel source and an outlet port which is connectable in fluid communication with a high pressure fuel injection pump; providing a motor for driving the fuel transfer pump for drawing fuel through the inlet port from the fuel source and pumping pressurized fuel out the outlet port; measuring a fuel pressure at a location which is in fluid communication with the outlet port; controlling an operating speed of the motor driving the fuel transfer pump as a function of the measured fuel pressure for defining a closed loop pressure control mode for controlling the measured fuel pressure to a target fuel pressure; measuring a current utilized in operating the motor; comparing the measured current to a predefined threshold current value; correlating the measured current to at least one anomalous condition when indicated by the comparison step; and switching from the closed loop pressure control mode for controlling the operating speed of the motor as a function of the measured fuel pressure to a current control mode for controlling the operating speed of the motor as a function of the measured current when the measured current is correlated by the correlation step to at least the one anomalous condition.
In another aspect, an embodiment of the invention provides a method for minimizing current inrush to a fuel transfer pump upon start up; the method comprising: providing a fuel transfer pump having an inlet port which is connectable in fluid communication with a fuel source and an outlet port which is connectable in fluid communication with a high pressure fuel injection pump; providing a motor for driving the fuel transfer pump for drawing fuel through the inlet port from the fuel source and pumping pressurized fuel out the outlet port; measuring a fuel pressure at a location which is in fluid communication with the outlet port; controlling an operating speed of the motor driving the fuel transfer pump as a function of the measured fuel pressure and a moving fuel pressure; measuring a current utilized in operating the motor; comparing the measured current to a predefined threshold current value; and ramping up the current utilized in operating the motor when the measured current is below the predefined threshold current value as indicated by the comparison step and ramping down the current utilized in operating the motor when the current is above the predefined threshold current value as indicated by the comparison step for providing the moving fuel pressure until the moving fuel pressure reaches a target fuel pressure.
In another aspect, an embodiment of the invention provides a fuel transfer pump system for delivering fuel to a high pressure pump of a fuel injection system, the fuel transfer pump system comprising: a fuel transfer pump having an inlet port which is connectable in fluid communication with a source of fuel and an outlet port which is connectable in fluid communication with a high pressure fuel injection pump; a motor for driving the fuel transfer pump for drawing fuel through the inlet port from the fuel source and pumping pressurized fuel out the outlet port at a target fuel pressure; means for measuring fuel pressure at a location in fluid communication with the outlet port of the fuel transfer pump; means for measuring current utilized in operating the motor; and a controller operatively coupled to the motor and connected in signal communication with the fuel pressure measuring means and the current measuring means, the controller being configured to adaptively switch between a closed loop pressure control mode for controlling an operating speed of the motor for obtaining the target fuel pressure as a function of the measured fuel pressure to a current control mode for controlling the operating speed of the motor as a function of the measured current when the measured current is correlated to at least one anomalous condition based on a comparison between the measured current and a predefined threshold current value.
In a further aspect, an embodiment of the invention provides a non-transitory microcontroller-readable memory containing microcontroller-executable instructions that, when executed by a processor, cause the processor to perform a multi-mode control method of a motor driving a pump, the method comprising: controlling an operating speed of a motor driving a pump for pressurizing fluid as a function of a measured pressure of the pressurized fluid for defining a closed loop pressure control mode for obtaining a target fluid pressure; and switching from the closed loop pressure control mode to a current control mode for controlling the operating speed of the motor as a function of a measured current utilized in operating the motor when the measured current is indicative of at least one anomalous condition.
Accordingly, it should be apparent that numerous modifications and adaptations may be resorted to without departing from the scope and fair meaning of the claims as set forth herein below following the detailed description of the invention.